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Molecularity

Posted: Sun Mar 08, 2020 11:38 pm
by Payton Kammerer 2B
I'm a little confused on the definition of molecularity. Or I suppose, the definition of "species"
Is a species a single molecule, or is it a single type of molecule? I may be confused because in biology, a species is a type of organism, but this definition seems to have little to do with that. In an elementary step in which two NO molecules collide, is that one or two species?

Re: Molecularity

Posted: Mon Mar 09, 2020 8:31 am
by Brian_Ho_2B
Molecularity accounts for both the number of different types of species as well as their stoichiometric coefficients. For instance, if an elementary step had something like: 2A + B --> something, the molecularity is termolecular, because in total, there are three molecules involved.

Re: Molecularity

Posted: Mon Mar 09, 2020 8:32 am
by Justin Sarquiz 2F
A species in this case refers to the number of reactants. In the example you gave, this is bimolecular. The number of moles of reactants determines the molecularity.

Re: Molecularity

Posted: Mon Mar 09, 2020 8:34 am
by Robin Cadd 1D
The textbook defines molecularity as the number of reactant moles, atoms, or ions taking part in a specified elementary reaction.

Re: Molecularity

Posted: Mon Mar 09, 2020 9:12 am
by Christineg1G
Molecularity would be the number of molecules or species in an elementary step, and also determine the rate. Rate law for each elementary steps comes directly from molecularity.